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Jongmin Jo,Woosik Sim,Hanju Cha 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This paper proposed reactive power variation (RPV) strategy using positive feedback (PF) to identify unintentional islanding condition of distributed generations (DGs) and cease the successive operation of them. The concept in this paper uses the relationship between the shift of point of common coupling (PCC) frequency and the injected reactive power after islanding occurrence. The structure of the proposed RPV method has a constant reactive power component and a certain reactive power term due to PF using the frequency deviation between the rated frequency and the measured frequency. When islanding occurs, PF increases continuously the positive or negative reactive power in order to deviate PCC frequency outside over/under threshold levels, where PF reduces significantly detection time. The proposed RPV strategy is verified in experiments through 1.7kW 3-level T-type inverter. Detection times of islanding are measured to 53ms and 150ms in over/under threshold levels, respectively.
Md Ahanur Reza,Myungjin Choi,Joongsu Lee,Woosik Jo,Seungchun Park 한국버섯학회 2010 한국버섯학회지 Vol.8 No.4
Auricularia auricula-judae has long been used as food and traditional remedies in Asian countries such as Korea and China. In this study, we evaluated the in vitro anti-tumor activity of various fractions from the ethanol extracts of Auricularia auricula-judae using various tumor cell lines. To do this, the mesh of Auricularia auricula-judae was mixed with 70% ethanol and heated at 1000C for 6 hrs and ethanol extract (ETOH) was collected. Ethanol extract was fractionated with dichloromethane (DCM), ethyl acetate, n-butanol and a water extract at room temperature as well as concentrated in a vacuum concentrator at a controlled temperature(<500C). The P388D1 macrophage and Sarcoma 180, human NSCLC NCI H358 (bronchioalveolar) and SNU1 cells (Gastric carcinoma) were cultured in RPMI. As the results, the cytotoxicity of the fractional extracts decreased significantly (P<0.05) in a dose-dependent manner. Dichloromethane extract (1 mg/ml) was the highest (P<0.05) in all experimental cell lines. There was also a significantly different sensitivity (P<0.05) among the P388D1, Sarcoma 180, NCI H358 and SNU1 cells for the fractional extracts. According to IC50 values, the most potent cytotoxic activity of dichloromethane fraction was found in Sarcoma 180 and NCI H358 cell lines. Butanol fraction appeared more cytotoxic to SNU1 cell line and water fraction had the highest cytotoxicity in P388D1 cell line. We did not find any significant difference between MTT and SRB assays in their ability to estimate cytotoxicity in all cell lines. Our findings suggest a potent antitumor activity of various fractions from the ethanol extracts of Auricularia auricula-judae depending on the solvent fractions and tumor cell lines. Further in vitro and in vivo studies will provide more information on the active compounds responsible for these activities and their potential as an anti-cancer remedy.